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GeneralRe: duplicate icons of SSD drive in windows explorer Pin
RickZeeland17-Nov-21 5:51
mveRickZeeland17-Nov-21 5:51 
JokeRe: duplicate icons of SSD drive in windows explorer Pin
Richard MacCutchan17-Nov-21 5:54
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GeneralRe: duplicate icons of SSD drive in windows explorer Pin
OriginalGriff17-Nov-21 6:07
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GeneralRe: duplicate icons of SSD drive in windows explorer Pin
Southmountain17-Nov-21 6:47
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GeneralRe: duplicate icons of SSD drive in windows explorer Pin
Gary Wheeler17-Nov-21 6:16
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GeneralRe: duplicate icons of SSD drive in windows explorer Pin
Southmountain17-Nov-21 11:30
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GeneralRe: duplicate icons of SSD drive in windows explorer Pin
Southmountain18-Nov-21 5:39
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GeneralOld and new - apparently a difference of only 306,240.90$ Pin
CodeWraith17-Nov-21 5:18
MemberCodeWraith17-Nov-21 5:18 
Modernizing an old computer design is a weird thing. First you strip away all anachronisms and look what's left.

In the case of the original Elf from 1976 that was the processor itself. By pure chance, I got hands on a CDP1802B, which also already existed in 1976, but it was the faster version which used to cost more. It hums along at 6MHz without breaking a sweat, giving me almost four times the performance of the original Elf. I don't have any means on the breadboard to carefully monitor the processor's core voltage and temperature, but overclocking the processor is possible and I may yet squeeze considerably more out of very old silicon.

Toggle switches (or hex keypads) and LED address and data displays are gone, but there is still an interesting aspect about them. The original Elf had no ROM to boot it. Instead, the switches and displays acted as DMA devices and allowed to enter the program manually before letting the processor start executing anything. A modern Elf can have an all RAM configuration, like the original. Why not copy the contents from a ROM to RAM using the same DMA mechanism after a reset? It's still the same old Elf and no typing involved to get that thing running. Plus keeping the advantage of not having a ROM awkwardly floating around in your 64k memory map.

Now, we still need some I/O. For the time being that is a serial port and a VT52 or VT100 terminal (actually an old PC running TeraTerm). That was not part of the old Elf concept, because hooking up a 80$ computer to a terminal that costs at least ten times as much seemed a bit silly. However, that option was added later for those who somehow got their hands on a terminal. The cool thing was, that the Elf never required a UART for serial communication. Serial data was sent and received by the processor itself with carefully timed software routines at 300 baud. Well, Zwölf does it the same way, but I rewrote these routines a little so that they now send and receive at 19200 baud. 38400 baud are possible, but the little processor can't keep up yet when the terminal sends packets of data during a XMODEM upload. The problem is, that there is only very little time to actually do anything with the received data before the UART on the other side already sends the next byte. Still, even at 19200 baud I can load a program faster than with an old C64 floppy drive. Indeed, I'm comfortably in the mid range of the C64's floppy accelerators. Not so bad for a crutch that only has to be sufficient until I have something better.

Up to here we have mostly taken stuff away from the old Elf. Now let's finally add something. RAM. Lot's of it. In 1976 RAM chips were slow, had only a tiny capacity and cost more than their weight in gold. That's why the original Elf only had 256 bytes of RAM. Barely sufficient for the simple trainer it originally was, but it kept the price for your own computer under 100$.

With only a very modest amount of simple logic chips I can access fairly modern SRAMs with a capacity of 512 kb each and up to a total of 16 Mb. Of course the processor can't access so much memory without banking, but a little speciality of the processor (which is often seen as a disadvantage) allows me to do the bank switching without the processor noticing it. I can call code anywhere at any time without having to fear any problems. The code loaded to each memory page now is something similar to a DLL. And this opens up a lot of possibilities for a serious operating system, something also unheard of for the original Elf.

Turns out that modernizing the old ELF is more about taking things away than adding things and about the only thing that was not available in 1976 was fast enough RAM at an affordable price. I was looking for the schematics of the original Elf in archived issues of Popular Electronics magazine. The old magazines were full of ads for computers like the Altair. In one ad for the Imsai 8080, they proudly announced that this computer was expandable up to one megabyte of banked memory. For that, the Zwölf needs only two memory chips for about 11 bucks.
The Imsai needed 16 S-100 cards at only 3900 Dollars each, assembled and tested or a bit cheaper as kits. Plus a truly huge power supply. That's about 63000 Dollars, just for the RAM and the power supply, 306,240.90 Dollars today, adjusted for inflation. I don't know how fast they used to run their 8080, but the Zwölf can outperform the old monster and even run on batteries, despite being mostly made of components from the same time. And it even costs less than the original Elf without adjusting for inflation.

I'm really having fun here. Smile | :)
I have lived with several Zen masters - all of them were cats.

His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.

GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
fgs196317-Nov-21 5:49
Memberfgs196317-Nov-21 5:49 
GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
Mike Hankey17-Nov-21 5:53
professionalMike Hankey17-Nov-21 5:53 
GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
Gary Wheeler17-Nov-21 6:14
MemberGary Wheeler17-Nov-21 6:14 
GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
Mike Hankey17-Nov-21 6:31
professionalMike Hankey17-Nov-21 6:31 
GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
Richard MacCutchan17-Nov-21 6:54
mveRichard MacCutchan17-Nov-21 6:54 
GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
Mike Hankey17-Nov-21 7:00
professionalMike Hankey17-Nov-21 7:00 
GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
  Forogar  17-Nov-21 7:57
professional  Forogar  17-Nov-21 7:57 
GeneralRe: Old and new - apparently a difference of only 306,240.90$ Pin
Gary Wheeler17-Nov-21 8:10
MemberGary Wheeler17-Nov-21 8:10 
GeneralVisual Studio and git disconnect Pin
Michael Breeden17-Nov-21 5:12
MemberMichael Breeden17-Nov-21 5:12 
AnswerRe: Visual Studio and git disconnect Pin
Mircea Neacsu17-Nov-21 6:16
mvaMircea Neacsu17-Nov-21 6:16 
GeneralRe: Visual Studio and git disconnect Pin
Michael Breeden17-Nov-21 7:39
MemberMichael Breeden17-Nov-21 7:39 
GeneralLow-Code-No-Code Bloatware Pin
Member 1484049617-Nov-21 2:11
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GeneralRe: Low-Code-No-Code Bloatware Pin
den2k8817-Nov-21 2:24
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GeneralRe: Low-Code-No-Code Bloatware Pin
Member 1484049617-Nov-21 2:38
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GeneralRe: Low-Code-No-Code Bloatware Pin
Member 1532961317-Nov-21 2:26
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GeneralRe: Low-Code-No-Code Bloatware Pin
Member 1484049617-Nov-21 2:33
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GeneralRe: Low-Code-No-Code Bloatware Pin
Member 1532961317-Nov-21 2:45
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